In a wireless local area network it is occasionally useful to perform sounding measurements of the communications environment between the access point and the wireless stations. These sounding measurements may provide data for use in beamforming and multiple input multiple output (MIMO) antenna operations. It is often desirable for an access point to request sounding information from multiple stations in parallel in order to obtain this information while maintaining singular communication link conditions.
Currently, an access point may request a sounding from a station by sending an announce message followed by a null data packet (NDP) sounding message directed to that station. This procedure may be repeated for each station, which can be time consuming and inefficient and may result in an unacceptable delay between the sounding measurements performed at each of the stations.
Thus, there are general needs for apparatus and efficient methods for an access point to request that multiple stations compute sounding measurements with minimal time delay between measurements.